Ubuntu is considered by many as being the leading edge distribution (distro), and was well ahead of Windows 8 in offering a touch friendly interface. Personally, I don't like it, but many thousands of others do.

openSUSE is RPM based, (Redhat package manager), still regarded as a strong upgrade mechanism, but different.

Each one has it's own "repositories" which should be used for additional applications as required. Do not attempt to use applications built for Windows on a Linux distro. Some can with something called "wine", but it's generally not easy and unnecessary, as Linux has literally thousands of free applications that will cover every normal computer chore you wish to do.

Yo will find when using a Linux distro, all the common applications that you need are pre-loaded. Things like Libre Office, Firefox, Thunderbird and so on.

Generally, anti-virus software and anti-malware software are not necessary, as there are only a couple of proof of concept viruses that have ever been successfully written and I've never heard of a Linux computer suffering from such problems.

As Fruit Bat /\0/\ suggests, run the distro first from a live CD/DVD to see if they are compatible with your computer. They've come a long way and again generally speaking, you shouldn't have any issues. It will also allow you to evaluate each and see which one you feel comfortable with.